1. Field of the Invention
The present invention relates to an apparatus for and a method of obtaining processing information for fitting lenses in an eyeglass frame and an eyeglass grinding machine.
2. Description of the Related Art
The adjustment of glasses is generally effected by making the distance between the optical centers of the lenses coincide with the pupillary distance (PD). For this purpose, the distance between the geometrical centers of the lens frame portions, (FPD), is usually obtained, and, from this FPD value and the PD value, the adjustment amount (the amount of displacement of the optical center of the lens from the geometrical center thereof) is calculated.
Conventionally, eyeglass lenses have been processed using the adjustment amount calculated on the assumption that both the frame and the lenses are plane surfaces.
In practice, however, various factors, such as the inclination of the eyeglass frame, the lens thickness and the lens curve, have to be taken into account, which means errors are inevitable in the above calculation. This is particularly true of a large-sized frame with a large amount of warp. Such errors may be corrected to some extent by a skilled operator. However, the intuition of the operator alone cannot help to obtain a satisfactory degree of precision.
This invention has been made in view of the problem mentioned above. It is an object of this invention to provide an apparatus for and a method of obtaining processing information for fitting lenses in an eyeglass frame and an eyeglass grinding machine, which allows the adjustment amount to be previously calculated so that the distance between the optical centers of the processes lenses may exactly coincide with the designated PD value, irrespective of the configuration of the frame and lenses.